Ch. 32 - 33 – Sponges, Cnidarians, & Ctenophores

What is an invertebrate?An animal without a backbone.

What are some examples?Animals are classified by their shape or

symmetry.What is symmetry?

Arrangement of body parts around a central axis.

Types of Symmetry

1. Asymmetrical – an organism without a definite shape.Ex. Sponge

2. Radial symmetry – an organism that can be divided into similar halves by any plane that passes through its longitudinal axis.Ex. hydra

3. Bilateral symmetry – is an organism that can be divided into similar halves by only one specific plane passing through its longitudinal axis.Ex. Humans, spiders, fish

Parts of an organisms’ surface1. Posterior – lower end of the organism

Ex. Feet of humans2. Anterior – upper end of the organism.

Ex. Head of a human3. Dorsal – top surface of an organism.

Ex. Back on a human4. Ventral – bottom surface.

Ex. Belly of a human

Organisms DevelopmentOrganism develop from a zygoteThen into an embryoNext is a blastula – a hollow ball

of cellsFinal the blastula caves in and

forms a depression called a blastopore. Once the blastula forms a blastopore it is now called a gastrula.

3 Germ Layers1. Ectoderm – outside layer of

cellsEx. Skin

2. Endoderm inside layer of cellsEx. Organs

3. Mesoderm – middle layer of cellsEx. Muscles

Porifera (phylum)Sponges

No gastrula stageNo true organsSessile – don’t moveVery colorful

Features of a spongeOsculum – top opening of a sponge

A sponge is hollow in the middleThe sponge’s hollow cavity is lined

with collar cells, which have flagella.

The collar cells are used to filter out food. Water and food enter the sponge through its pores then pass back out its osculum. Sponges are filter feeders.

Amebocytes transport the food from the collar cells to the rest of sponge.

Sponges have the ability to reproduce sexually or asexually; sponges carry both egg and sperm cells.

Sponges reproduce asexually by producing buds called gemmules.

Sponges have the ability to regrow missing parts. What is this called?Regeneration

Most sponges have both sperm and egg cells, some have separate sexes.

Hermaphrodite is an organism with both egg and sperm cells.

Video Clip

Cnidaria (phylum)Example: jellyfish, hydra, coralHave endoderm & ectoderm

layersAll live in water (mainly marine)Have stinging cells called

nematocystHave a hollow gutHave tentacles

2 body shapes of Cnidarians1. Polyp

Sessile and vase-like shape2. Medusa

Swimming and bell shapeAll cnidarians use their tentacles

to capture and paralyze their prey with a coiled stinger called a nematocyst.

3 Classes of Cnidarians1. Hydrozoa – Hydra

Both polyps and medusa shapes

2. Scyphozoa – jellyfishMostly medusa

3. Anthozoa – coralsOnly as polyps

Hydrozoa (class)Hydra use their nematocyst to capture

prey and engulf the whole prey into their gastro vascular cavity. They only have one opening (mouth and anus).

Asexual reproduction of small buds occurs during warm weather.

Sexual reproduction occurs mainly in the fall.

Hydra are hermaphrodites.Video Clip

Scyphozoa (class)Mostly medusaJellyfish have poisonous

tentacles with nematocyst, also.Several humans been seriously

injured and even killed from jellyfish off the coast of Australia.

Video Clip

Anthozoa (class)Only polypSea anemones are polyps along

rocks.Clown fish swim around in their

tentacles. The clown fish is protected from the tentacles by a chemical in their skin that doesn’t allow the nematocyst to fire.

Video Clip

3 main body cavities of organisms1. Acoelomate – without a body cavity.

Ex. Hydra, planaria2. Pseudocoelomate – false body cavity.

No true digestive system. The gut is suspended in fluid, not muscle.Ex. Roundworm

3. Coelomate – a true body cavity.Ex. Earthworm, insects, humans, ect.

Rotifera (phylum)Rotifers

Free-swimmingMarine and freshwaterCilia along its mouth, which is used

to sweep food into its mouth.Looks like a spinning wheel as it

moves.Video Clip